Java 如何在android中解析JSON API

我正在开发一个应用程序，我有一个Json api，我需要在recyclerview中填充它。这是一个新闻api（不是来自newsapi.org）。我是解析json的初学者。然而，我试着去做，但除了一个空屏幕外，什么也没来

Json api是

我已附上代码

MainActivity.java java news_item.xml

来自的repsonse是一个JSON对象，而不是数组。所以请使用下面的代码正确获取新闻条目

private void jsonRequest() {
        jsonObjectRequest = new JsonObjectRequest(Request.Method.GET,JSON_URL, null, new Response.Listener<JSONObject>() {
            @Override
            public void onResponse(JSONObject response) {
                JSONArray articles = response.optJSONArray("articles") 
                JSONObject jsonObject = null;

                for (int i=0;i<articles.length();i++){
                    try {
                        jsonObject = articles.getJSONObject(i);
                        News news = new News();
                        news.setAuthor(jsonObject.getString("author"));
                        news.setDescription(jsonObject.getString("description"));
                        news.setTitle(jsonObject.getString("title"));
                        news.setPublishedAt(jsonObject.getString("publishedAt"));
                        newsList.add(news);
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                }
                setUpRecyclerView(newsList);
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {

            }
        });

        requestQueue = Volley.newRequestQueue(MainActivity.this);
        requestQueue.add(jsonObjectRequest);
    }

private void jsonRequest（）{
jsonObjectRequest=newJSONObjectRequest（Request.Method.GET，JSON_URL，null，new Response.Listener（））{
@凌驾
公共void onResponse（JSONObject响应）{
JSONArray articles=response.optJSONArray（“articles”）
JSONObject JSONObject=null；
对于（int i=0；iAdded Request.Method.GET和null到构造函数，你现在可以检查吗？当我打开应用程序时，它只显示3个新闻项，但在json文件中它有很多项。为什么？请将你的ActivityMain.xml代码添加到问题中。布局可能有一些问题。新闻列表中有多少项？我添加了activity_main.xml。在Json中，它包含的totalResult为38。我认为问题是在for循环中使用response.length（），它的大小为3，现在在答案中替换为articles.length（）。请检查。
    <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:background="#000"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".activities.MainActivity">
    <TextView
        android:id="@+id/textView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="15dp"
        android:layout_marginLeft="15dp"
        android:text="Top Headlines"
        android:textColor="#fff"
        android:textSize="22dp"
        android:textStyle="bold"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="1.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/news"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="1.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView"
        app:layout_constraintVertical_bias="0.034" />
</androidx.constraintlayout.widget.ConstraintLayout>

import android.content.Context;
import android.graphics.drawable.Drawable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.recyclerview.widget.RecyclerView;

import com.bumptech.glide.Glide;
import com.bumptech.glide.load.DataSource;
import com.bumptech.glide.load.engine.DiskCacheStrategy;
import com.bumptech.glide.load.engine.GlideException;
import com.bumptech.glide.load.resource.drawable.DrawableTransitionOptions;
import com.bumptech.glide.request.RequestListener;
import com.bumptech.glide.request.RequestOptions;
import com.bumptech.glide.request.target.Target;
import com.news.newsapp.R;
import com.news.newsapp.activities.Utils;
import com.news.newsapp.model.News;

import java.util.List;

public class Adapter extends RecyclerView.Adapter<Adapter.MyViewHolder>{

    private Context context;
    private List<News> news;

    public Adapter(Context context, List<News> news) {
        this.context = context;
        this.news = news;
    }

    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view;
        LayoutInflater inflater = LayoutInflater.from(context);
        view = inflater.inflate(R.layout.news_item, parent, false);
        return new MyViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull final MyViewHolder holder, int position) {
        final MyViewHolder holders =  holder;
        News model = news.get(position);

        RequestOptions requestOptions = new RequestOptions();
        requestOptions.placeholder(Utils.getRandomDrawbleColor());
        requestOptions.error(Utils.getRandomDrawbleColor());
        requestOptions.diskCacheStrategy(DiskCacheStrategy.ALL);
        requestOptions.centerCrop();

        Glide.with(context)
                .load(model.getUrlToImage())
                .apply(requestOptions)
                .listener(new RequestListener<Drawable>() {
                    @Override
                    public boolean onLoadFailed(@Nullable GlideException e, Object model, Target<Drawable> target, boolean isFirstResource) {
                        holder.progressBar.setVisibility(View.GONE);
                        return false;
                    }

                    @Override
                    public boolean onResourceReady(Drawable resource, Object model, Target<Drawable> target, DataSource dataSource, boolean isFirstResource) {
                        holder.progressBar.setVisibility(View.GONE);
                        return false;
                    }
                })
                .transition(DrawableTransitionOptions.withCrossFade())
                .into(holder.imageView);

        holder.author.setText(news.get(position).getAuthor());
        holder.description.setText(news.get(position).getDescription());
        holder.title.setText(news.get(position).getTitle());
        holder.time.setText("\u2022" + Utils.DateToTimeFormat(model.getPublishedAt()));
        holder.publishedAd.setText(Utils.DateFormat(model.getPublishedAt()));
    }

    @Override
    public int getItemCount() {
        return news.size();
    }

    public static class MyViewHolder extends RecyclerView.ViewHolder{

        TextView author, title, description, time, publishedAd;
        ImageView imageView;
        ProgressBar progressBar;
        public MyViewHolder(@NonNull View itemView) {
            super(itemView);
        }
    }
}

import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;

import org.ocpsoft.prettytime.PrettyTime;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.Random;

public class Utils {

    public static ColorDrawable[] vibrantLightColorList =
            {
                    new ColorDrawable(Color.parseColor("#ffeead")),
                    new ColorDrawable(Color.parseColor("#93cfb3")),
                    new ColorDrawable(Color.parseColor("#fd7a7a")),
                    new ColorDrawable(Color.parseColor("#faca5f")),
                    new ColorDrawable(Color.parseColor("#1ba798")),
                    new ColorDrawable(Color.parseColor("#6aa9ae")),
                    new ColorDrawable(Color.parseColor("#ffbf27")),
                    new ColorDrawable(Color.parseColor("#d93947"))
            };

    public static ColorDrawable getRandomDrawbleColor() {
        int idx = new Random().nextInt(vibrantLightColorList.length);
        return vibrantLightColorList[idx];
    }

    public static String DateToTimeFormat(String oldstringDate){
        PrettyTime p = new PrettyTime(new Locale(getCountry()));
        String isTime = null;
        try {
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'",
                    Locale.ENGLISH);
            Date date = sdf.parse(oldstringDate);
            isTime = p.format(date);
        } catch (ParseException e) {
            e.printStackTrace();
        }

        return isTime;
    }

    public static String DateFormat(String oldstringDate){
        String newDate;
        SimpleDateFormat dateFormat = new SimpleDateFormat("E, d MMM yyyy", new Locale(getCountry()));
        try {
            Date date = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'").parse(oldstringDate);
            newDate = dateFormat.format(date);
        } catch (ParseException e) {
            e.printStackTrace();
            newDate = oldstringDate;
        }

        return newDate;
    }

    public static String getCountry(){
        Locale locale = Locale.getDefault();
        String country = String.valueOf(locale.getCountry());
        return country.toLowerCase();
    }
}

    public class News {
    private String author;
    private String title;
    private String description;
    private String url;
    private String publishedAt;
    private String urlToImage;

    public News() {
    }

    public News(String author, String title, String description, String url, String publishedAt, String urlToImage) {
        this.author = author;
        this.title = title;
        this.description = description;
        this.url = url;
        this.publishedAt = publishedAt;
        this.urlToImage = urlToImage;
    }

    public String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }

    public String getPublishedAt() {
        return publishedAt;
    }

    public void setPublishedAt(String publishedAt) {
        this.publishedAt = publishedAt;
    }

    public String getUrlToImage() {
        return urlToImage;
    }

    public void setUrlToImage(String urlToImage) {
        this.urlToImage = urlToImage;
    }
}

    <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools">
    <androidx.cardview.widget.CardView
        android:id="@+id/cardView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="11dp"
        android:layout_marginRight="11dp"
        android:layout_marginTop="7dp"
        android:layout_marginBottom="7dp"
        app:cardBackgroundColor="#000"
        app:cardElevation="@dimen/cardview_default_elevation"
        app:cardCornerRadius="10dp">
        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content">
            <ImageView
                android:id="@+id/img"
                android:layout_width="match_parent"
                android:layout_height="200dp"
                android:scaleType="centerCrop"
                android:transitionName="img"
                tools:ignore="UnusedAttribute"/>
            <ImageView
                android:id="@+id/shadow_image"
                android:layout_width="match_parent"
                android:layout_height="80dp"
                android:layout_alignBottom="@+id/img"
                android:src="@drawable/bottom_shadow"/>
            <ProgressBar
                android:id="@+id/progress_load_image"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginTop="70dp"
                style="@android:style/Widget.ProgressBar.Small"/>
            <TextView
                android:id="@+id/author"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:drawablePadding="10dp"
                android:ellipsize="end"
                android:maxLines="1"
                android:textColor="#fff"
                android:singleLine="true"
                android:layout_marginRight="160dp"
                android:layout_marginLeft="10dp"
                android:text="Author"
                android:gravity="bottom"
                android:layout_alignLeft="@+id/title"
                android:layout_alignStart="@+id/title"
                android:layout_alignRight="@+id/layoutDate"
                android:layout_alignTop="@+id/layoutDate"
                android:layout_alignEnd="@+id/layoutDate"/>

            <FrameLayout
                android:id="@+id/layoutDate"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_below="@+id/img"
                android:background="#fff"
                android:padding="5dp"
                android:layout_alignParentRight="true"
                android:layout_marginRight="20dp"
                android:layout_marginTop="-50dp">

                <ImageView
                    android:src="@drawable/ic_date"
                    android:layout_width="18dp"
                    android:layout_height="18dp"
                    android:layout_marginLeft="5dp"
                    android:layout_marginRight="5dp"/>

                <TextView
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:id="@+id/publishedAt"
                    android:textColor="#606060"
                    android:layout_marginLeft="27dp"
                    android:layout_marginRight="10dp"
                    android:text="01 January 1999"/>
            </FrameLayout>

            <TextView
                android:id="@+id/title"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_below="@id/img"
                android:layout_alignParentStart="true"
                android:layout_alignParentLeft="true"
                android:layout_alignParentRight="true"
                android:layout_marginStart="16dp"
                android:layout_marginLeft="16dp"
                android:layout_marginTop="10dp"
                android:text="Title"
                android:textColor="#fff"
                android:textSize="17sp" />

            <TextView
                android:id="@+id/desc"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_below="@id/title"
                android:layout_alignParentStart="true"
                android:layout_alignParentLeft="true"
                android:layout_alignParentRight="true"
                android:layout_marginStart="16dp"
                android:layout_marginLeft="16dp"
                android:layout_marginTop="5dp"
                android:text="Desc"
                android:textColor="#fff" />

            <TextView
                android:id="@+id/source"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_below="@id/title"
                android:layout_alignParentStart="true"
                android:layout_alignParentLeft="true"
                android:layout_alignParentRight="true"
                android:layout_marginStart="16dp"
                android:layout_marginLeft="16dp"
                android:layout_marginTop="26dp"
                android:text="Source"
                android:textColor="#fff" />
            <TextView
                android:id="@+id/time"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_below="@id/title"
                android:layout_marginLeft="16dp"
                android:layout_marginRight="16dp"
                android:layout_marginTop="46dp"
                android:text="Time"
                android:textColor="#fff" />
        </RelativeLayout>
    </androidx.cardview.widget.CardView>
</FrameLayout>

private void jsonRequest() {
        jsonObjectRequest = new JsonObjectRequest(Request.Method.GET,JSON_URL, null, new Response.Listener<JSONObject>() {
            @Override
            public void onResponse(JSONObject response) {
                JSONArray articles = response.optJSONArray("articles") 
                JSONObject jsonObject = null;

                for (int i=0;i<articles.length();i++){
                    try {
                        jsonObject = articles.getJSONObject(i);
                        News news = new News();
                        news.setAuthor(jsonObject.getString("author"));
                        news.setDescription(jsonObject.getString("description"));
                        news.setTitle(jsonObject.getString("title"));
                        news.setPublishedAt(jsonObject.getString("publishedAt"));
                        newsList.add(news);
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                }
                setUpRecyclerView(newsList);
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {

            }
        });

        requestQueue = Volley.newRequestQueue(MainActivity.this);
        requestQueue.add(jsonObjectRequest);
    }